Intgeration with i18n

Undefined index: #properties in i18n_field_field_widget_form() (line 254 of /var/www/www.my_site.com/sites/all/modules/i18n/i18n_field/i18n_field.module).

function i18n_field_field_widget_form in i18n_field.module line 254
the function trying get the widget properties from $element array

if ($element['#properties']['empty_option']) {
...
}

but you return from
hook_field_widget_form line 51 multiple_selects.module
$element without #properties index
because you put the $properties in $element['value'] and not into $element['#properties']
I think you need add #properties index befor return the $element from multiple_selects_field_widget_form line 51
like this
$element['#properties'] = $properties;

Sorry for my english ))!